1. Field of the Invention
The present invention relates to phenylgycines and derivatives thereof, 1,4-aminobenzoyl compounds, and phenyl pyrazolinones as cure accelerators for anaerobically curable compositions.
2. Brief Description of Related Technology
Anaerobic adhesive compositions generally are well-known. See e.g., R. D. Rich, “Anaerobic Adhesives” in Handbook of Adhesive Technology, 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and reference cited therein. Their uses are legion and new applications continue to be developed.
Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Oftentimes, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures.
Desirable anaerobic cure-inducing compositions to induce and accelerate cure may include saccharin, toluidines, such as N,N,-diethyl-p-toluidine (“DE-p-T”) and N,N-dimethyl-o-toluidine (“DM-o-T”), acetyl phenylhydrazine (“AHN”), maleic acid (“MA”), and quinones, such as napthaquinone and anthraquinone. See e.g., Loctite U.S. Pat. No. 3,218,305 (Krieble), U.S. Pat. No. 4,180,640 (Melody), U.S. Pat. No. 4,287,330 (Rich) and U.S. Pat. No. 4,321,349 (Rich).
Saccharin and APH have been used as standard cure accelerator components in anaerobic adhesive cure systems since the inception of the technology, and has been well studied in that connection. Hitherto, it was believed that the nitrogen-hydrogen bond off the heterocycle ring was necessary to achieve performance under anaerobic conditions, as early studies substituting the hydrogen with an alkyl group proved to be ineffective. See F. J. Boerio et al., “Surface-Enhanced Raman Scattering from Model Acrylic Adhesive Systems”, Langmuir, 6, 721-27 (1990), in which it is stated “[t]hese salts [of saccharin] are thought to be important factors in the curing reaction of the adhesive.”
Recently, Loctite (R&D) Ltd. developed an anaerobic adhesive composition, which is defined by (a) a (meth)acrylate component; and (b) an anaerobic cure-inducing composition comprising an anaerobic curative within the following structure:
where A and A1 may be selected from O and N; and
R, R1, R2 and R3 may be the same or different and are selected from alkyl, alkenyl, cycloalkyl, cycloalkenyl, and aryl, having from 1 to about 30 carbon atoms, and may be substituted or interrupted with a heteroatom, and heterocyclic structures; or
R1 and R3 taken together may join to form a cyclic structure having from about 20 to about 28 ring atoms, and together represent dialkyl substituted polyether structures that may be substituted or interrupted with the trithiadiaza pentalene structure, which itself may or may not be substituted by A1, R2, or R3, as defined above. See U.S. Pat. No. 6,583,289 (McArdle).
There is an on-going desire to find alternative technologies for accelerating the cure of anaerobic curable compositions to differentiate existing products and provide supply assurances in the event of shortages or cessation of supply of raw materials. Accordingly, it would be desirable to identify new materials, which function as accelerators in the cure of anaerobic curable compositions.